Field of the Invention
The present invention relates generally to heat exchanger systems and arrangements, such as a helical heat exchanger tube assembly, and in particular to an improved coil key separating device and attachment therefor for use in a helical heat exchanger tube assembly having inner and outer coils.
Description of the Related Art
Swimming and relaxing in a pool or spa are popular pastimes. Swimming pools, both public and private, offer relief from the heat while also offering an opportunity for social gatherings and fun. Several types of swimming pools and spas exist, including in-ground pools, above-ground pools, wading pools for small children, spas, hot tubs, and whirlpools. Swimming pools and spas can be located outdoors, as in the back yard of a house or at a public area, or indoors, as in a hotel pool, for example. Further, swimming pools can be found in various sizes, ranging from a small, above-ground pool that is only a few feet in depth, to a large, Olympic-sized pool, designed for competitive swimming and/or diving. Similarly, spas, hot tubs, and whirlpools can be found in various sizes.
Many pools, especially indoor pools, are typically heated for the comfort of users. Spas, hot tubs, and whirlpools are also heated for the comfort of users, as well as for therapeutic purposes of users. Since most indoor pools, including hotel pools and community pools, remain open to users year-round, and since most spas also remain open year-round, it is necessary for the heat exchanger that heats the pool or spa water to be able to work reliably with little maintenance or repairs.
Due to the necessity of swimming pool pumps to move or turn over the entire volume of pool water through the pool filter several times a day, any full-flow heat exchanger must handle a high flow rate and, thus, high velocity of the water flowing through the heat exchanger. This high velocity poses several problems, as the high velocity could cause vibration of the heat exchanger coil tubes that heat the water. The coil tubes have a natural spring resonant frequency and are prone to vibration. The vibration could be in the hundreds or even thousands of cycles per second. Over time, the vibrations may rub the material in the sidewall of the tube and create a hole, thereby allowing the gas contained therein to escape and water to enter the tube.
Due to the corrosive chlorine and pool sanitation chemicals used to treat swimming pools, including inorganic chlorinating agents, such as calcium hypochlorite, lithium hypochlorite, sodium hypochlorite, and organic chlorinating agents, such as trichloroisocyanuric acid, potassium dichloroisocyanurate, or sodium dichlorocyanurate in anhydrous or dihydrate forms, the tube material may include an alloy, such as titanium or a high alloy stainless steel, that can withstand these chemicals without fouling or corrosion, and to ensure continued service over time. The above alloys are typically costly materials. In order to maximize heat transfer and minimize expense, thin wall tubing is commonly used in swimming pool and spa heat exchangers. Alloys such as these develop a hard film oxide coating, which helps to prevent the corrosion caused by chlorine and other pool sanitation chemicals. This coating is abrasive, which requires additional precautions to prevent tube damage caused by the wall tubing rubbing together.
Because the heat exchanger coil typically has an inner coil assembly arranged concentrically within an outer coil assembly, it is desirable to centrally align the inner coil assembly relative to the outer coil assembly for optimum heat transfer and uniform fluid velocity. Furthermore, it is desirable to maintain an equal spacing between the individual coils of the inner and outer coil assemblies. Various methods and devices for centering the coil assemblies and maintaining a separation between the individual coils have been developed. For example, silicone rubber can be injected between the coils at various intervals. Additionally, rubber or plastic bumpers may be inserted between the coils. In other embodiments, long strips of material are inserted axially between the inner and outer coil assemblies during their formation or after they are formed.
Within the prior art, U.S. Pat. No. 7,721,360 to Bernardi et al., incorporated herein in its entirety, describes a dog bone-shaped coil key separator device for use in a swimming pool heat exchanger. With reference to FIGS. 4-5 of the present application, the separator device 17 has an inner portion, a curved middle portion, and an outer portion. The outer portion has rounded outer edges to facilitate gripping and twisting the separator device 17 during installation between the coils of an outer coil 19 of the heat exchanger coil assembly. The inner portion of the separator device 17 is substantially flat so that it rests against the side of an inner coil 18 of the heat exchanger coil assembly. The curved middle portion rests between an upper and lower section of the outer coil 19. The separator device 17 is inserted between adjacent portions or sections of the outer coil 19, such that the outer portion and the inner portion of the separator device 17 are positioned longitudinally with respect to the adjacent sections of the outer coil during insertion. Once the inner portion comes into contact with the inner coil 18, the outer portion of the separator device 17 is twisted clockwise or counterclockwise into a locked position, such that the curved middle portion of the separator device 17 rests between the adjacent sections of the outer coil 19. In the locked position, the separator device 17 substantially prevents the adjacent coils of the outer coil 19 from vibrating against each other, the adjacent coils of the inner coil 18 from vibrating against each other, and the outer coil 19 from vibrating against the inner coil 18.
However, existing methods require substantial care and time to assemble, and, in some cases, must be subject to or include baking or curing time for setting up the material before the heat exchanger coils can be used. Further, many of these methods are also costly to manufacture and may not promote water flow between the coils.